On the role of interaction anisotropy in vibrational relaxation of HF and HCl by Ar

A coupled states quantum scattering study of vibrational relaxation in Ar HF and Ar + HCl collisions is presented. The energy transfer in these syst ems exhibits a quasiresonant character resulting in a strongly inverted rot ational population of the diatomic molecules after collision. The high anis otropy of interaction is shown to be determining the quasiresonant vibratio nal energy transfer by favoring the population of high rotational energy le vels. The role of interaction anisotropy in atom-diatomic molecule collisio ns is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.